Cellular telephones and PDAs (Personal Digital Assistants) are coming into widespread use. As a result of this, users exchange information between a plurality of such devices more frequently.
Hitherto, when exchanging information as described above, information is sent and received by connecting devices with each other via a cradle or a cable or by allowing infrared transmitters/receivers to face each other.
However, wired connection makes the operation troublesome and complicated, and also, a connector compatible with each device type must be prepared.
In infrared communication, if the user inadvertently passes through the infrared transmission channel, communication is interrupted.
It has been suggested that wireless communication is performed between a plurality of devices by using a wireless LAN (Local Area Network) or a short-distance wireless LAN, for example, Bluetooth®.
However, when exchanging information, for example, between a PDA owned by the user and a device installed in front of the user, the user is unable to know whether communication can be made between the devices unless he/she actually perform communication. In this manner, when performing wireless communication, the user is unable to know a communication distance at which information can be exchanged by connecting devices.